Method of manufacturing a large- or medium-sized wheel disk and a product manufactured thereby

ABSTRACT

A method of manufacturing a large- or medium-sized wheel disk including using a punch or die in a first step of ironing a blank of a flat plate to a first-stage product. The first-stage product having a cylindrical rising portion with an axially non-constant thickness. The rising portion includes a thick portion located at a tip portion of the rising portion and a thickness-reduced portion which is a remaining portion of the rising portion excluding the thick portion. During the first step, only a portion of the blank corresponding to the thickness-reduced portion is ironed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a national phase application based on the International PatentApplication No. PCT/JP2013/083025 filed Dec. 10, 2013, claiming priorityto Japanese patent application No. 2012-270125 filed Dec. 11, 2012, theentire contents of both of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method of manufacturing a large- ormedium-sized wheel disk manufactured from a blank of a flat plate and aproduct manufactured thereby.

BACKGROUND

Patent Document 1 discloses a conventional method of manufacturing alarge- or medium-sized wheel disk including steps of: (a) ironing ablank of a flat plate to a first-stage product of a cup-likeconfiguration having a cylindrical rising portion; and (b) diametricallyenlarging the cylindrical rising portion of the first-stage product to aconical rising portion thereby forming the first-stage product to asecond-stage product.

However, there are the following problems with the conventional methodof manufacturing a large- or medium-sized wheel disk:

More particularly, in Patent Document 1, at the ironing step, anentirety of a portion of the blank corresponding to the rising portionof the first-stage product is ironed. However, in Patent Document 1,there is no teaching or suggestion about taking the next, second step ofdiametrically enlarging the rising portion into consideration whenconducting the first step of ironing. Therefore, there is thepossibility that cracks may be caused in the product material whendiametrically enlarging the first-stage product to the second-stageproduct, because after having ironed the product material, the length ofthe ironed portion of the product material is significantly decreased.

RELATED ART DOCUMENT Patent Document

Document 1: Patent Publication No. JP 2010-58126

BRIEF SUMMARY Problems to be Solved

An object of the invention is to provide a method of manufacturing alarge- or medium-sized wheel disk and a product manufactured thereby,capable of preventing cracks from being generated in comparison toconventional cases.

Means for Solving the Problems

The present invention achieves the above object is as follows:

(1) A method of manufacturing a large- or medium-sized wheel diskcomprising:

-   -   a first step of ironing a blank of a flat plate as a material to        a first-stage product having a cylindrical rising portion of an        axially non-constant thickness using a punch and a die, the        first-stage product including a thick portion located at a tip        portion of the rising portion and a thickness-reduced portion        which is a remaining portion of the rising portion excluding the        thick portion,    -   wherein during the first step, only a portion of the blank        corresponding to the thickness-reduced portion of the rising        portion is ironed.        (2) A method of manufacturing a large- or medium-sized wheel        disk according to item (1) above, further comprising:    -   a second step conducted after the first step, of diametrically        enlarging the rising portion of the first-stage product to form        a conical rising portion thereby forming the first-stage product        to a second-stage product; and    -   a third step conducted after the second step, of forming the tip        portion of the second-stage product to a final disk flange        configuration thereby forming the second-stage product to a        third-stage product.        (3) A method of manufacturing a large- or medium-sized wheel        disk according to item (1) above, wherein at the first step, the        blank of a flat plate is firstly press-formed to a configuration        of a dish or a cup, and then is ironed using the punch and the        die.        (4) The first-stage product for a large- or medium-sized wheel        disk manufactured using the method according to item (1) above.

Technical Advantages

According to the method of manufacturing a large- or medium-sized wheeldisk of item (1) above, the following technical advantage can beobtained:

The first-stage product manufactured at the first step includes thethick portion. Therefore, when the rising portion of the first-stageproduct is diametrically enlarged after the first step, less cracks aregenerated than in conventional cases.

According to the method of manufacturing a large- or medium-sized wheeldisk of item (2) above, the following technical advantage can beobtained:

Since the second step and the third step are conducted after the firststep, a second-stage product and a third-stage product having no crackscan be produced.

According to the method of manufacturing a large- or medium-sized wheeldisk of item (3) above, the following technical advantages can beobtained:

At the first step, the blank of a flat plate is firstly press-formed tothe configuration of a dish or a cup, and then is ironed by using thepunch and the die. As a result, it is possible to more stably form thefirst-stage product than in a case where the blank of a flat plate isdirectly formed to the first-stage product. Further, a load loaded ontoan ironing apparatus can be decreased.

According to the first-stage product for a large- or medium-sized wheeldisk of item (4) above, the following technical advantages can beobtained:

The first-stage product includes the thick portion. Therefore, after thefirst step, when the rising portion of the first-stage product isdiametrically enlarged, and less cracks are generated than inconventional cases a crack can be less generated than in theconventional case.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a process diagram of a method of manufacturing a large- ormedium-sized wheel disk according to an embodiment of the presentinvention, where

(a) illustrates a disk material of a square, flat plate,(b) illustrates a blank of a flat plate,(c) illustrates a first step,(d) illustrates a second step,(e) illustrates a third step,(f) illustrates a step for forming a hub hole by punching,(g) illustrates a step for forming a hub bolt hole by punching,(h) illustrates a step for forming a vent window by punching, and(i) illustrates a wheel disk.

FIG. 2 is a cross-sectional view of an ironing apparatus at a statebefore the first step, used in the method of manufacturing a large- ormedium-sized wheel disk according to an embodiment of the presentinvention, where hatchings of the ironing apparatus are omitted in orderto clarify the drawing.

FIG. 3 is a cross-sectional view of the ironing apparatus at a stateafter the first step, used in the method of manufacturing a large- ormedium-sized wheel disk according to an embodiment of the presentinvention, where hatchings of the ironing apparatus are omitted in orderto clarify the drawing.

FIG. 4 is a cross-sectional view of a diameter-enlarging apparatus at asecond step, used in the method of manufacturing a large- ormedium-sized wheel disk according to an embodiment of the presentinvention, where hatchings of the diameter-enlarging apparatus areomitted in order to clarify the drawing.

FIG. 5 is a cross-sectional view of a forming apparatus at a third step,used in the method of manufacturing a large- or medium-sized wheel diskaccording to an embodiment of the present invention, where hatchings ofthe forming apparatus are omitted in order to clarify the drawing.

FIG. 6 is a cross-sectional view of a press-drawing apparatus, forpress-drawing the blank of a flat plate to a configuration of a dish,used in the method of manufacturing a large- or medium-sized wheel diskaccording to an embodiment of the present invention, where hatchings ofthe drawing press are omitted in order to clarify the drawing.

FIG. 7 is a cross-sectional view of a large- or medium-sized wheel diskmanufactured by using the method of manufacturing a large- ormedium-sized wheel disk according to an embodiment of the presentinvention.

FIG. 8 is a cross-sectional view of an alteration of the ironingapparatus used at the first step, in the method of manufacturing alarge- or medium-sized wheel disk according to an embodiment of thepresent invention.

FIG. 9 is a cross-sectional view of another alteration of the ironingapparatus used at the first step, in the method of manufacturing alarge- or medium-sized wheel disk according to an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A method of manufacturing a large- or medium (middle)-sized wheel diskaccording to an embodiment of the present invention will be explainedbelow with reference to FIGS. 1-9.

First, a large- or medium-sized wheel disk (which may be called merely awheel disk, hereinafter) 10 manufactured using the method ofmanufacturing a large- or medium-sized wheel disk according to anembodiment of the present invention will be explained. The wheel disk 10is a large- or medium-sized wheel disk for use in a truck or a bus, etc.The wheel disk 10 may be a wheel disk for use in a car for private useor a vehicle for business or industry. The wheel disk 10 is manufacturedfrom a disk material of a flat plate shown in FIG. 1. The wheel disk 10is not a cast wheel. The wheel disk 10 is, for example, made from steel.Alternatively, the disk 10 may be made from aluminum alloy, titaniumalloy or magnesium alloy, etc. The wheel disk 10 is manufacturedindependently of an annular rim (not shown, a portion of a wheel holdinga tire) and is coupled with the rim by welding, a rivet, or an adhesiveto construct a wheel.

As illustrated in FIG. 7, the wheel disk 10 includes a hub couplingportion (which may be called a flat plate portion) 20 fixed to a hub(not shown) and a rising portion (which may be called a side wall) 30rising from a radially outer portion of the hub coupling portion 20 inan axial direction of the disk (i.e., in an axial direction of thewheel).

Usually, the hub coupling portion 20 is like a flat (includingsubstantially flat) plate. When the hub coupling portion 20 is like aflat plate, the hub coupling portion 20 is perpendicular (includingsubstantially perpendicular) to an axial direction of the disk. Sincethe hub coupling portion 20 is not thinned by ironing, the hub couplingportion 20 is the same (including substantially the same) thickness as athickness of a blank 4 of a flat plate. A hub hole 21 and a hub bolthole 22 are formed at the hub coupling portion 20.

The hub hole 21 is located at a central portion of the wheel disk 10 ina radial direction of the wheel disk (i.e., in a radial direction of thewheel).

Plural hub bolt holes 22 are equi-spaced in a circumferential directionof the disk (i.e., in a circumferential direction of the wheel) on asingle circle.

The wheel disk 10 (or the wheel) is fixed to a hub (not shown) of thevehicle by causing a hub bolt (not shown) extending from the hub of thevehicle to pass through the hub bolt hole 22 and threading a hub nut(not shown) to the hub bolt.

The rising portion 30 includes a conical portion 31 and a disk flange32.

The conical portion 31 is connected to the radially outer portion of thehub coupling portion 20. The conical portion 31 extends from theradially outer portion of the hub coupling portion 20 inclined in adirection outward in the radial direction of the disk and away from theradially outer portion of the hub coupling portion 20 in the axialdirection of the disk so that a rising amount of the rising portion 30is increased in the axial direction of the disk.At least a portion of the conical portion 31 is thinned by ironing andis made smaller in thickness than the blank 4 of a flat plate. A ventwindow 33 is formed at the conical portion 31.The disk flange 32 is located at an end portion of the rising portion 30in a direction in which the rising portion 30 rises (i.e., in the axialdirection of the disk). The disk flange 32 is located at a radiallyouter portion of the rising portion 30. The disk flange 32 iscylindrical so as to fit to a radially inner surface of the rim (notshown).The disk flange 32 may be thinned by ironing, etc. so as to be smallerin thickness than the blank 4 of a flat plate. The disk flange 32 maynot be thinned by ironing.The wheel disk 10 is welded to the rim (not shown) at the disk flange32.

Next, a method of manufacturing the wheel disk 10 will be explained.

As illustrated in FIG. 1, the method of manufacturing the wheel disk 10is a method manufacturing the wheel disk 10 from the blank 4 of a flatplate.

As illustrated in FIGS. 1 (a) and 1 (b), the blank 4 is manufactured bypunching a square (including substantially square) disk material 2 of aflat plate to a circular (including substantially circular) flat plateor a substantially square flat plate four corners of which are cut in ashape of an arc.

The method of manufacturing the wheel disk 10 includes:

(i) a first step (an ironing step) illustrated in FIG. 1 (c), of ironingthe blank 4 using a punch 51 and a die 52 to a first-stage product 11which includes a cylindrical rising portion 11 a having a non-constantthickness and a flat portion 11 b; (ii) a second step (a diametricallyenlarging step) illustrated in FIG. 1 (d), of diametrically enlargingthe rising portion 11 a of the first-stage product 11 to form a conicalrising portion 12 a thereby forming the first-stage product 11 to asecond-stage product 12; and (iii) a third step (a second ironing step)illustrated in FIG. 1 (e), of forming the tip portion 12 c of the risingportion 12 a of the second-stage product 12 to a final disk flangeconfiguration (shown in FIG. 7) thereby forming the second-stage product12 to a third-stage product 13.

The first step (the ironing step) of item (i) above will be explainedbelow.

(i-1) As illustrated in FIGS. 2 and 3, the first step is a step forironing the blank 4 of a flat plate to the first-stage product 11 usingthe punch 51 and the die 52.(i-2) As illustrated in FIG. 3, the first-stage product 11 is a cup-likeproduct including the flat portion 11 b and the cylindrical risingportion 11 a having a non-constant thickness. The first-stage product 11includes a thick portion 11 c (which may be called a thickness-remainingportion) located at a tip portion (an end portion opposite the flatportion 11 b) of the rising portion 11 a and a thickness-reduced portion11 d which is a remaining portion of the rising portion 11 excluding thethick portion 11. The thick portion 11 c is provided at an entirecircumference of the tip portion of the rising portion 11 a.(i-3) The first step is a step where not only ironing but also drawingare conducted. The drawing of the first step is a drawing for formingthe blank 4 to a cup-like configuration.(i-4) The first ironing step is conducted simultaneously over an entirecircumference of the first-stage product by pressing. The ironing may beconducted one or more times including replacement of a die.(i-5) As illustrated in FIG. 2, at the first step, the ironing isconducted using an ironing apparatus 50 which is a press machine havingthe punch 51 and the die 52.The ironing may be conducted after the drawing shown in FIG. 6 has beenconducted.The die 52 has a protrusion 54 protruding inwardly in a radial directionof a cylindrical bore 52 a at an inner surface of the die and irons theblank 4 by the protrusion 54.The punch 51 is cylindrical. A convex-concave surface 53 is formed at aside surface of the punch 51 opposing the protrusion 54 of the die 52.The convex-concave surface 53 is a surface whose radial space from theprotrusion 54 of the die 52 is not constant. Alternatively, asillustrated in FIG. 8, the convex-concave surface 53 may be a surface530 whose radial space from the protrusion of the die is constant. Asillustrated in FIG. 9, the convex-concave surface 53 may be a surface531 whose radial space from the protrusion 54 of the die 52 gradually(smoothly) changes narrower (or wider). In order to make a space betweenthe protrusion 54 of the die 52 and the side surface of the punch 53opposing the protrusion 54 of the die 52 narrower than a thickness ofthe blank 4 having a constant thickness, the convex-concave surface 53of the punch 51 may be provided with at least one convex portion 53 aconvex toward the protrusion 54 of the die 52 relative to a portion(i.e., a concave portion 53 b) located adjacent the convex portion 53 aof the side surface of the punch 51 in an axial direction and/or acircumferential direction of the punch 51.A protruding amount of the convex portion 53 a may be constant ornon-constant between opposite ends of the convex portion 53 a. In a casewhere plural convex portions 53 a are provided, protruding amounts ofthe respective convex portions 53 a may be equal or not equal to eachother. The convex portion 53 a may be provided at a portion or allportions of the side surface of the punch 51 opposing the protrusion 54of the die 52.In the axial direction of the side surface of the punch 51, one convexportion 53 a and a concave portion 53 b located adjacent the one convexportion 53 a are connected by an inclined surface 53 c which is notperpendicular to the axial direction of the punch 51. An angle betweenthe inclined surface 53 c and an axial direction of the side surface ofthe punch 51 is set at an angle desirably equal to or smaller than 60degrees, and more preferably equal to or smaller than 45 degrees. Aninclination angle of each inclined surface 53 c may be constant or maychange gradually.

(i-6) The die 52 is constructed of an outer die having the cylindricalbore 52 a. The punch 51 is constructed of an inner punch which is movedinto or out from the cylindrical bore 52 a of the outer die 52 in theaxial direction of the cylindrical bore 52 a. The convex-concave surface53 is formed at an outside surface of the inner punch. As illustrated inFIG. 3, a convex-concave configuration can be formed at only an insidesurface of the rising portion 11 a of the first-stage product 11 by theironing conducted using the inner punch 51 and the outer die 52.

(i-7) At the first step, the blank 4 is ironed by moving the punch 51relative to the die 52 in the axial direction of the blank 4 only (i.e.,in the axial direction of the cylindrical bore 52 a or the wheel disk10). In FIG. 3, “A1” shows a moving direction of the punch 51. Anupper-lower relationship between the punch 51 and the die 52 shown inFIG. 1 (c) may be opposite an upper-lower relationship between the punch51 and the die 52 shown in FIGS. 2 and 3.

(i-8) As illustrated in FIG. 3, at the first step, a portion of theblank 4 corresponding to the thickness-reduced portion 11 d may beironed. A portion of the blank 4 corresponding to the thick portion 11 cmay be ironed to an extent that the thick portion 11 c has a thicknessequal to or larger than 90% of the thickness of the blank 4 after thefirst step, or may not be ironed. This is because a certain amount of“elongation of the material” of the thick portion 11 is kept at thefirst step, so that crack of the material is suppressed from happeningduring the diameter-enlarging at the second step. Most preferably, thethick portion 11 c may not be ironed from the viewpoint of preventing acrack from being generated. In a case where the thick portion 11 c isnot ironed, the thickness of the thick portion 11 c is the same(including substantially the same) as a thickness of the hub couplingportion 20 or is larger than the thickness of the hub coupling portion20.

(i-9) At the first step, the blank 4 of a flat plate may firstly pressedto a configuration of a dish or a cup (i.e., the blank may be pre-formedto a configuration of a dish or a cup), and then is ironed using thepunch 51 and the die 52 to thereby manufacture the first-stage product11. As illustrated in FIG. 6, the pre-forming is a press-drawing formingconducted using a press-drawing apparatus 60 having a punch 61 and a die62.

The second step (the diametrically enlarging step) of item (ii) abovewill be explained below.

(ii-1) The second step is conducted after the first step.(ii-2) As illustrated in FIG. 4, the second-stage product 12 includes aflat portion 12 b and the conical rising portion 12 a having anon-constant thickness, and has a configuration of a dish.(ii-3) At the second step, the rising portion of the first-stage productis diametrically enlarged by forcibly inserting a punch 71 having aconical portion into the rising portion of the first-stage product 11.At the second step, not only diametrically enlarging but also forgingmay be conducted at a stroke end of the punch 71.(ii-4) At the second step, the diametrically enlarging is conductedusing a diameter-enlarging apparatus 70 which is a press machineinstalled with a punch 71 and a die 72.(ii-5) The die 72 is constructed of an outer die having a conical bore72 a. The punch 71 is constructed of an inner punch which is moved intoor out from the conical bore 72 a of the outer die 72 in an axialdirection of the conical bore 72 a (i.e., in the axial direction of thewheel disk 10).(ii-6) At the second step, the rising portion of the first-stage productto which a convex-concave configuration has been given is formedradially outwardly, whereby objective configuration and thicknessdistribution are obtained.(ii-7) The second step is conducted simultaneously over an entirecircumference of the product by pressing.(ii-8) At the second step, the rising portion 11 a of the first-stageproduct 11 is diametrically enlarged by forcibly moving the punch 71relative to the die 72 only in an axial direction of the rising portion11 a of the first-stage product 11 (i.e., in the axial direction of thewheel disk 10). In FIG. 4, “A2” shows a moving direction of the punch71. An upper-lower relationship between the punch 71 and the die 72shown in FIG. 1 (d) may be opposite an upper-lower relationship betweenthe punch 71 and the die 72 shown in FIG. 4.(ii-9) Diametrical enlarging at the second step is not limited to theenlarging using the press machine described above and may be conductedusing an expander (not shown), etc.

The third step of item (iii) above will be explained below.

(iii-1) The third step is conducted after the second step.(iii-2) As illustrated in FIG. 5, the third-stage product 13 includes aflat portion 13 b and a rising portion 13 a having a non-constantthickness, and has a configuration of a dish (including substantially adish).(iii-3) At the third step, drawing is conducted. At the third step, notonly the drawing but also ironing may be conducted. Further, at thethird step, only the ironing may be conducted.(iii-4) At the third step, the tip portion 12 c of the rising portion 12a of the second-stage product 12 is ironed, whereby the tip portion 12 cis formed to a configuration of disk flange 32. At the third step, thetip portion 12 c of the rising portion 12 a of the second-stage product12 is ironed and raised, whereby objective outside diameter andthickness of the disk flange can be obtained.(iii-5) At the third step, ironing is conducted using a second apparatus80 which is a press machine installed with a punch 81 and a die 82.(iii-6) The die 82 is constructed of an outer die having a bore 82 a, avicinity of an open end of which is cylindrical. The punch 81 isconstructed of an inner punch which is moved into or out from the bore82 a of the outer die 82 in an axial direction of the bore 82 a (i.e.,in the axial direction of the wheel disk 10).(iii-7) The die 82 has an open end portion 82 b located at the open endof the bore 82 a and irons the end portion 12 c of the rising portion 12a of the second-stage product 12 by the open end portion 82 b.(iii-8) At the third step, an entire circumference of the second-stageproduct is simultaneously formed using the press machine.(iii-9) At the third step, the tip portion of the rising portion 12 a ofthe second-stage product 12 is ironed by forcibly moving the punch 81relative to the die 82 in an axial direction only of the rising portion12 a of the second-stage product 12 (i.e., in the axial direction of thewheel disk 10). In FIG. 5, “A3” shows a moving direction of the punch81. An upper-lower relationship between the punch 81 and the die 82shown in FIG. 1 (e) may be opposite an upper-lower relationship betweenthe punch 81 and the die 82 shown in FIG. 5.(iii-10) At the third step, the drawing conducted using the pressmachine shown in FIG. 5 may be replaced by flow-forming, etc.(iii-11) At the third step, sizing by machining may be conducted afterthe drawing conducted using the press machine (or flow-forming, etc.)(iii-12) The third step (for forming the tip portion 12 c to the diskflange 32 configuration) may be conducted during the second step.

As illustrated in FIGS. 1( f), 1(g), 1(h) and 1(i), after the thirdstep, the wheel disk 10 may be manufactured by punching the third-stageproduct to thereby form the hub hole 21, the hub bolt hole 22 and thevent window 23.

Next, technical advantages of the present invention will be explained.In the present invention, at the first step, the portion of the blank 4corresponding to the thickness-reduced portion 11 d is ironed. Theportion of the blank 4 corresponding to the thick portion 11 c may notbe ironed or may be ironed such that the thick portion 11 c has athickness equal to or more than 90 percent of the thickness of the blank4. As a result, when the rising portion 11 a of the first-stage product11 is diametrically enlarged after the first step, and cracks can beprevented from being generated in comparison to conventional cases.

At the first step, the blank 4 of a flat plate is firstly pressed to theconfiguration of a dish or a cup, and then is ironed using the punch 51and the die 52. As a result, it is able to form the first-stage product11 more stably than in a case where the blank 4 of a flat plate isdirectly formed to the first-stage product 11. Further, a load loadedonto the ironing apparatus 50 can be decreased.

Since the second step and the third step are conducted after the firststep, the second-stage product 12, the third-stage product 13 and thelarge- or medium-sized wheel disk 10 where no cracks are generated canbe obtained.

Further, since the first-stage product 11 is formed by ironing at thefirst step, any pushing flaw of parts of a flow-forming machine can bemore suppressed from remaining at the surfaces of the first-stageproduct 11, the second-stage product 12, the third-stage product 13 andthe large- or medium-sized wheel disk 10 than in a case where thefirst-stage product 11 is formed by flow-forming.

The portion of the blank 4 corresponding to the thickness-reducedportion 11 d of the first-stage product is ironed at the first step. Theportion of the blank 4 corresponding to the thick portion 11 c is notironed or is ironed such that the thick portion 11 c has a thickness ofmore than 90 percent of the blank 4. As a result, when the risingportion 11 a of the first-stage product 11 is diametrically enlargedafter the first step, cracks can be suppressed in comparison withconventional cases.

If the blank is formed to the first-stage product by forging only, alarge load is necessary resulting in increased initial costs. Incontrast, in the present invention, since the blank is formed to thefirst-stage product by ironing, the forming load is significantlydecreased, thus, resulting in lower initial costs.

In the above explanation of the embodiment of the present invention, thefirst step, the second step and the third step are conducted in thatorder. However, the order of the steps is not limited to that order.More particularly, the third step may be conducted during the secondstep.

EXPLANATION OF REFERENCE NUMERALS

2 flat plate disk material

4 blank

10 wheel disk

11 first-stage product

11 a rising portion of the first-stage product

11 b flat portion of the first-stage product

11 c thick portion of the first-stage product

11 d thickness-reduced portion of the first-stage product

12 second-stage product

12 a rising portion of the second-stage product

12 b flat portion of the second-stage product

12 c tip portion of the rising portion of the second-stage product

13 third-stage product

13 a rising portion of the third-stage product

13 b flat portion of the third-stage product

20 hub coupling portion

21 hub hole

22 hub bolt hole

30 rising portion

31 conical portion

32 disk flange

33 vent window

50 ironing apparatus

51 punch

52 die

53, 530, 531 convex-concave surface

54 protrusion

60 drawing press

61 punch of the drawing press

62 die of the drawing press

70 diameter-enlarging apparatus

71 punch of the diameter-enlarging apparatus

72 die of the diameter-enlarging apparatus

80 disk flange forming press

81 punch of the disk flange forming press

82 die of the disk flange forming press

1. A method of manufacturing a large- or medium-sized wheel diskcomprising: a first step of ironing a blank of a flat plate as amaterial to a first-stage product having a cylindrical rising portion ofan axially non-constant thickness using a punch and a die, thefirst-stage product including a thick portion located at a tip portionof the rising portion and a thickness-reduced portion which is aremaining portion of the rising portion excluding the thick portion,wherein during the first step, only a portion of the blank correspondingto the thickness-reduced portion of the rising portion is ironed.
 2. Amethod of manufacturing a large- or medium-sized wheel disk according toclaim 1, further comprising: a second step conducted after the firststep, of diametrically enlarging the rising portion of the first-stageproduct to form a conical rising portion thereby forming the first-stageproduct to a second-stage product; and a third step conducted after thesecond step, of forming the tip portion of the second-stage product to afinal disk flange configuration thereby forming the second-stage productto a third-stage product.
 3. A method of manufacturing a large- ormedium-sized wheel disk according to claim 1, wherein at the first step,the blank of a flat plate is firstly press-formed to a configuration ofa dish or a cup, and then is ironed using the punch and the die.
 4. Thefirst-stage product for a large- or medium-sized wheel disk manufacturedusing the method according to claim
 1. 5. (canceled)